In building spaces in which objects and pictures are put on display, such as in exhibit areas of museums, building lobbies, office reception areas and showrooms, it is desirable to use light fixtures that can easily be removed and replaced by different type fixtures and in which the positions of the lights can be adjusted so that the lighting of the articles on display can be optimized when the exhibit is changed. It is also desirable to install the support systems and wiring for light fixtures in both new construction and renovation without installing the fixtures themselves, lest the fixtures be harmed during the stages of the construction or renovation after the support system and wiring are installed. Indeed, it is often advantageous to both install the fixtures and adjust them at the same time. Various lighting systems, such as high hat fixtures and track lighting, are suited to installation of the fixtures separately from the fixture mounting assembly and wiring but they are not always well-suited to some types of displays and to the architectural concepts of the space.
There is a need, for example, for lighting systems that are recessed into a ceiling and in which the fixtures can be easily and quickly removed and replaced and also adjusted to various lighting needs. For example, the same light mounting structure in a ceiling may be called upon to provide object lighting for one display and wall-wash lighting for another. It is known per se to adapt light fixtures to provide different forms of light by changing lamps, lenses, reflectors and shields, but it is sometimes more convenient and occasionally necessary to make the required changes when the fixtures are removed from their mounts. Also, it may be desirable at times to locate multiple mounts on regular spacings on a ceiling or in a slot recessed into a ceiling, and then be able to attach lighting fixtures to the mounts most advantageously located for the lighting requirements of the particular exhibit.